Several forms of sleep apnea have been identified. Obstructive sleep apnea (OSA) is caused by a blockage of the airway, usually when the soft tissue in the throat collapses and closes during sleep. Less common forms of sleep apnea include central sleep apnea (CSA), wherein the airway is not blocked but the brain fails to signal the muscles to breathe, and mixed apnea which, as the name implies, is a combination of OSA and CSA.
As shown in FIG. 1a, an air passage 140a of a patient 101a is open while the patient is in the awake state. The soft tissue components, including the soft palate 130a and the pharyngeal walls 132a of the air passage are supported by the underlying musculature to maintain the passageway in the open condition. During an obstructive sleep apnea event, illustrated in FIG. 1b, the air passage 140b of a patient 101b is partially or completely blocked by surrounding soft tissue 130b, 132b, which has collapsed due to the relaxation of the supporting musculature and has been displaced during sleep by gravity or other forces.
With each apnea event, the brain briefly arouses the sleeping person in order to resume breathing, but sleep is consequently extremely fragmented and of poor quality. Untreated, sleep apnea can cause high blood pressure, cardiovascular disease, memory problems, weight gain, impotency, and headaches. Moreover, untreated sleep apnea may be responsible for job impairment, motor vehicle crashes, and marital discord.
According to the National Institutes of Health, sleep apnea is very common, as common as adult diabetes, and affects more than twelve million Americans. The factors that increase the risk of having OSA include being male, overweight, and over the age of forty, but sleep apnea can strike anyone at any age, even children. Because of the lack of awareness by the public and healthcare professionals, the vast majority of patients remain undiagnosed and therefore untreated, despite the fact that this serious disorder can have significant consequences.
Attempts to provide an effective treatment for obstructive sleep apnea have yielded unsatisfactory results. For example, electrical stimulation of the soft palate has been suggested to treat snoring and obstructive sleep apnea. Such a teaching is found in Schwartz et al., “Effects of electrical stimulation to the soft palate on snoring and obstructive sleep apnea,” J. Prosthetic Dentistry, pp. 273-281 (1996). Devices to apply electrical stimulation are described in U.S. Pat. Nos. 5,284,161 and 5,792,067. Electrical stimulation to treat sleep apnea is also discussed in Wiltfang et al., “First results on daytime submandibular electrostimulation of suprahyoidal muscles to prevent night-time hypopharyngeal collapse in obstructive sleep apnea syndrome,” International Journal of Oral & Maxillofacial Surgery, pp. 21-25 (1999). Such devices are appliances requiring patient adherence to a regimen of use as well as subjecting the patient to discomfort during sleep and repeated arousals during deep sleep.
Continuous Positive Airway Pressure (CPAP) has recently been adopted as a useful, albeit cumbersome, means of preventing sleep apnea. CPAP delivers air into the airway through a specially designed nasal mask or pillows. The mask does not breathe for the patient; the flow of air creates enough pressure when the patient inhales to keep the airway open. In effect, a pneumatic splint is formed in the airway. CPAP is considered the most effective non-surgical treatment for the alleviation of snoring and obstructive sleep apnea. Compliance, however, is only 50%, as patients complain about discomfort from the mask, hoses, etc. and that the equipment requires maintenance. Additionally, patients complain of discomfort such as bloating, nasal drying, and dry eyes.
Surgical treatments have also been employed. One such treatment is uvulopalatopharyngoplasty (UPPP). UPPP is discussed, for example, in Harries et al., “The surgical treatment of snoring,” Journal of Laryngology and Otology, pp. 1105-1106 (1996), which describes removal of up to 1.5 cm of the soft palate. The use of UPPP in the treatment of snoring is assessed in Cole et al., “Snoring: A review and a Reassessment,” Journal of Otolaryngology, pp. 303-306 (1995). In that procedure, about 2 cm of the trailing edge of the soft palate is removed through the use of a scalpel, laser or other surgical instrument, thereby reducing the tendency of the soft palate to flutter between the tongue and the pharyngeal wall of the throat. The procedure is frequently effective to alleviate snoring but has demonstrated limited effectiveness in moderate or severe apnea. The procedure is painful and frequently results in undesirable side effects. In particular, the reduction of the soft palate compromises the ability of the soft palate to seal off nasal passages during swallowing and speech. In an estimated 25% of uvulopalatopharyngoplasty patients, fluid escapes from the mouth into the nose while drinking.
Uvulopalatopharyngoplasty (UPPP) may involve lasting discomfort. For example, scar tissue on the soft palate may present a continuing irritant to the patient. In addition, UPPP is not reversible and may induce adverse side effects not justified by the benefits of the surgery. Furthermore, UPPP is targeted to the correction of deficiencies associated with the palate only and does not address issues associated with the collapse of the tongue and lateral pharyngeal walls.
Radiofrequency ablation of the soft palate, or SomnoplastySM, is similar in concept to the Laser Assisted Uvulopalotopharyngoplasty (LAUP), although a different energy source is used, and thermal lesions are produced within the tissues, rather than using a laser to ablate the tissue surface. For that reason, radiofrequency ablation appears to be growing in popularity as an alternative to LAUP. The SomnoplastySM device is approved by the U.S. Food and Drug Administration (FDA) for radiofrequency ablation of palatal tissues for simple snoring and radiofrequency ablation of the base of the tongue for OSA. In some situations, radiofrequency ablation of the soft palate and base of tongue are performed together as a multi-level procedure. To date, the treatments alone or in combination have failed to provide relief to more than 50% of patients.
Another device intended to treat snoring or obstructive sleep apnea is comprised of several braided PET cylinders that are implanted to make the tissues of the tongue or uvula more rigid and less prone to deflection against the pharyngeal wall. The Pillar™ Palatal Implant System, marketed by Restore Medical of St Paul, Minn., is an implantable device that has been cleared by the FDA 510(k) process. The device is a cylindrical-shaped segment of braided polyester filaments that is permanently implanted submucosally in the soft palate. The labeled indication of the device is as follows: “The Pillar™ Palatal Implant System is intended for the reduction of the incidence of airway obstructions in patients suffering from mild to moderate OSA (obstructive sleep apnea).” The device has been associated with a number of adverse side effects, including extrusion, infection, and patient discomfort.
The Repose™ device, marketed by Influent Medical LLC of Concord, N.H., involves the use of a titanium screw that is inserted into the posterior aspect of the mandible at the floor of the mouth. A loop of suture is passed through the tongue base and attached to the mandibular bone screw. The Repose™ procedure achieves a suspension or hammock of the tongue base making it less likely for the base of the tongue to collapse against the posterior pharyngeal wall during sleep. The reported duration of beneficial effects afforded by the implant is less than a year. Due to the high activity of the tongue during wakefulness, the suture component of this device has been shown in some cases to act as a “cheese cutter” to the tongue, causing device failure and requiring subsequent removal.
Magnets have also been considered as implants for the treatment of obstructive sleep apnea. These devices are currently being evaluated in clinical trials. One serious complication than can potentially occur with these implants is implant migration or flipping of the magnets which can cause acute airway closure.
In summary, electrical stimulation of the musculature within the airway is ineffective since it arouses the patient from deep sleep. CPAP effectively manages OSA but has a very low patient compliance (less than 50% of patients continue the treatment). Surgical techniques and implants have also been evaluated, yet still do not provide a satisfactory and lasting solution. No one device seems capable of treating the multi-causal problem of obstructive sleep apnea. What is needed are methods and devices that reduce the burden of managing obstructive sleep apnea through a minimally invasive approach that provides long term and effective results. Ideally, the treatment should be adjustable and removable if necessary. The inventions described herein provide such treatments that offer long-term relief of OSA.